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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Exploring Geology Chapter 6 Volcanoes and Volcanic Hazards
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06.00.a Before 1980 eruption Mount St. Helens After 1980 eruption During eruption
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Crater Vent where magma erupted Commonly a hill or mountain Can be erupted from fissure or depression, so not a hill Observe some characteristics of a volcano 06.01.a Can erupt lava or ash
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06.01.b Erosion of flow Fissure feeds a lava flow Hill was not over a vent (so not a volcano) Example of such a hill that is not a volcano Observe how a hill capped by volcanic rocks can form. Is it a volcano?
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06.01.c Shield Volcano Scoria Cone Types of Volcanoes: Part 1
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06.01.c Volcanic Dome Composite Volcano Types of Volcanoes II
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06.02.a Observe these types of eruptions Dome Lava flow Lava fountain Eruption column
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06.02.b2 Dissolved gas held in magma by pressure What happens when you open a soda? Under less pressure, gas forms bubbles Released gas propels eruption and forms ash How Do Gases Affect Magma? Opening top releases dissolved gas held in by pressure
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06.02.c How Does Viscosity Affect Eruptions? More viscous: difficult to flow and traps gas Less viscous: flows easier and gas can escape
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06.03.a Scoria Cones and Basalt Flows: Rock Types Nonvesicular basalt Vesicular basalt Scoria
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06.03.a Features of Lava Flows AA lava Lava tubes Pahoehoe lava
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